1. Technical Field.
The invention relates to a method and device for adjusting the selecting out of winnowings in the manufacture of smokable products, in particular cigarettes.
2. Description of the Related Art.
For a long time it has been common in the industrial production of cigarettes to re-sift the cut tobacco before manufacturing the rod, in order to separate out larger tobacco particles, undesirable in the tobacco rod of a cigarette, which in the following shall be referred to as “winnowings”.
In the case of conventional cigarettes in manufacturing machines, this sifting process is always performed in the sifter of the rod manufacturing machine. There are various techniques for separating out winnowings, which are based primarily on the different masses of the winnowings on the one hand, and the tobacco lamina desired in the cigarette—in the following called lamina for short—on the other.
The essence of the common methods is that the tobacco particles are spatially divided into light and heavy particles by the effect of gravity and/or an additional force, e.g. an influencing stream of air.
A known separating technique is described in DE-PS 11 57 523, in which tobacco particles mechanically ejected by a Winnover cylinder pass through different trajectories, strike two impact metal sheets and are thus separated.
In the method as set forth in GB-PS 971 736, tobacco particles are propelled through a stream of air, whereby the lighter particles are pulled along and the heavier particles fall down onto a sieve. A stream of air flowing through the sieve from below can again separate the lighter particles from the heavier ones.
GB-PS 998 476 shows a method in which the tobacco particles fall in a continuous stream through a stream of air introduced transversely. The tobacco particles are deflected to different degrees due to their different masses and are thus separated.
In the method as set forth in DE-PS 11 67 241, tobacco particles are accelerated by a casting-off cylinder and pass through different trajectories due to their mass. The heavier tobacco particles, generally the stems, fall into a stem box. The lighter tobacco particles fall through a transverse or reverse sifting stream of air, which separates the heavier particles still present from the lighter ones.
U.S. Pat. No. 3,092,117 shows tobacco particles being pneumatically conveyed in a first stream of air. A second stream of air deflects the lighter particles and thus separates two fractions from each other.
U.S. Pat. No. 3,173,861 shows tobacco particles falling down into an adjustable stream of air substantially perpendicular to the falling direction. The heavier particles are not deflected or hardly deflected and so reach a lower collecting opening. Adjustment is provided in the sense that the basic settings of the machine can be changed, so as to adjust the separation method to different tobaccos.
DE-PS 21 06 134 shows a method in which tobacco particles are guided past a suction cylinder, such that lighter particles remain stuck to the suction cylinder while heavier particles fall downwards. For the basic settings of the separating mechanism, two different air supplies are provided.
Lastly, DE 42 42 325 A1 shows a method in which tobacco particles are separated from each other in a cyclone separator.
If the separated material separated using one of the methods as set forth in the prior art is examined by weighing and sieving the separated out material collected over a certain period of time, this reveals that—depending on the setting of the separating process—winnowings and lamina are almost always present in different quantities. Using an optimum setting, however, it should be possible to separate all the winnowings but none of the lamina.
Detailed examinations of the chronological progression of separated quantities of winnowings and lamina, using a suitable sensor, have revealed the following:
The overall separation rates are often unstable with respect to a nominal value, such that in these unstable phases too few winnowings are separated, and the product quality therefore drops when namely separation drops below the nominal value, or too great a proportion of lamina is lost for manufacturing when separation rises above the nominal value and lamina are therefore separated out as winnowings.
In phases of stable separating in the overall quantity, it is not possible to respond to naturally varying winnowing proportions in the tobacco material supplied, i.e. the separation rate cannot be retro-adjusted.
The separation setting on rod machines as set forth in the prior art is also not suitable for rapid intervention, the manufacturing process generally has to be interrupted to change the basic setting, in order to change the separating process, i.e. the means of separating the winnowings from the stream of tobacco particles. In the currently common systems, for instance, when using an impact metal sheet as the separator element, the machine has to be stopped and the position of the impact metal sheet changed by means of its fixing screws. This interruption, however, disrupts the continuity of manufacture, and it is not possible to check the changed separation in the minutes following the adjustment, since the result cannot reflect the value for continuous production.
This applies even when the winnowings are continually monitored using the sensor as set forth in DE 199 48 559 C1.